We will create a low cost portable instrument for functional imaging of brain that can be used outside the hospital for emergency evaluation of stroke patients and in the classroom for monitoring the learning and mastery of tasks. Imaging of brain physiology has become a valuable tool in research and in the evaluation of clinical brain diseases. Both functional Magnetic Resonance Imaging (fMRI) and Evoked Response Potentials (ERP) (functional electroencephalography (fEEG)) have revealed the regional dynamics of brain function in response to mental activity and challenges. Both methods have limitations. Although MR methods can reveal functional chemical details about anatomic regions of the brain, the temporal resolution of these MR methods is limited and the environmental conditions of the magnet restrict the kinds of mental and physical tasks that can be performed by the patient under study. Although EEG methods have a time resolution much better than a second, the spatial information about brain function from EEG data must be inferred by indirect methods. In this project, we will develop an ultrasonic method of displaying cortical pulsatility, which is a surrogate of brain cortex perfusion. This system will be designed to provide brain perfusion maps that differentiate areas of normal, hyper- and hypo- pulsatility using a conspicuous contrast method. The temporal resolution of the method is near one second and the spatial resolution is near 1 cm. This brain cortex perfusion imaging system has applications in functional brain research, in stroke diagnosis and management and in the management of head trauma. It can be used on ambulatory patients and research subjects for prolonged periods. In addition to clinical applications, we plan to use this instrumentation to support research in learning and in mental disability research. This new ultrasonic method holds the promise of extremely low cost. Currently, ultrasound instruments with similar complexity can be purchased at prices affordable by primary care clinics.